(1) Field of the Invention
The present invention relates to a method for manufacturing a porous article for in vivo use.
(2) Description of the Related Art
Porous articles for in vivo use are suitably used as a substitute prosthetic material for hard tissues such as bones and joints. Porous articles are fixed in the body by allowing osseous tissues, etc., to enter therein. Ceramics, polymers, etc., are known raw materials for the porous articles usable in vivo (i.e., biomedical porous articles). From the viewpoint of improving mechanical properties such as strength, ductility, etc., stainless steel, cobalt-chromium alloys, pure titanium, titanium alloys and like biocompatible metallic materials are also widely used.
Examples of known methods for manufacturing a biomedical porous article comprising such a metallic material include: forming a porous article by spraying and depositing titanium powder or the like onto a base material under high temperature and high pressure; obtaining a porous article by sintering a metallic material formed into bead-like shapes to evaporate a binder therein; obtaining a porous article by removing or deforming a portion of a metal base material by etching or blasting. However, since connections between pores cannot be obtained in porous articles obtained by these methods, if such a porous article is used as a bone prosthetic material, osseous tissues can barely enter the porous article, and therefore satisfactory linkage between the porous article and the bone cannot be obtained.
To overcome this problem, Japanese Unexamined Patent Publication No. 1995-184987 discloses a porous article wherein a plurality of metallic thin plates each having many pores are laminated, and the plurality of metallic thin plates are adhered to one another by heating. In this porous article, it is possible to control the alignment of pores by positioning the metallic thin plates while putting one on top of another. Therefore, a strong linkage between the porous article and tissues can be obtained by accelerating introduction of osseous tissues, etc., into the porous article.
However, in the porous article disclosed in Japanese Unexamined Patent Publication No. 1995-184987, positioning of the metallic thin plates while laminating is complicated and there is a risk of the metallic thin plates separating. Furthermore, in order to vary the porosity, additional metallic thin plates having different pore formation patterns must be prepared, and thus there is scope for improvement.